CA1061007A - Electric circuit arrangements incorporating cathode ray tubes - Google Patents
Electric circuit arrangements incorporating cathode ray tubesInfo
- Publication number
- CA1061007A CA1061007A CA215,759A CA215759A CA1061007A CA 1061007 A CA1061007 A CA 1061007A CA 215759 A CA215759 A CA 215759A CA 1061007 A CA1061007 A CA 1061007A
- Authority
- CA
- Canada
- Prior art keywords
- anode
- potential
- cathode
- electron stream
- electron
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/488—Schematic arrangements of the electrodes for beam forming; Place and form of the elecrodes
Landscapes
- Cold Cathode And The Manufacture (AREA)
- Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
- Video Image Reproduction Devices For Color Tv Systems (AREA)
Abstract
Abstract of the Disclosure An electron gun assembly of a cathode ray tube comprises in the order named, a cathode, an apertured modulator electrode, a first and a second apertured anode and a third cylindrical focussing anode. The modulator electrode and the first anode are supplied with such potentials as to form a crossover of elec-trons therebetween and the second anode is supplied with such a lower positive potential than at the adjacent first and third anodes that electron stream emitted from the cathode is formed into a narrow beam of electrons and is allowed to enter the third anode at a small angle of beam spread and comes to a focus on the screen of the tube by the third anode to produce a spot of small cross-sectional area.
Description
The present invention relates to electric circuit arrangements of the kind incorporat:ing and arranged for the operation of cathode ray tubes of the type having a sealed evacuated envelope consisting oI` a bulb portion formed in the approximate shape Or a truncated cone and a cylindrical neck portion extend-ing substantially axially from the narrower end of the bulb portion, and containing an electron gun assembly, located within the neck portion, for pro-ducing a density-modulated stream of electrons, a phosphor screen carried within the bulb portion, at which the electron stream is directed to produce a spot of small crosx-sectional area. More particularly, it relates to the operation of cathode ray tubes Or the above-described type having an electron gun assembly of the type having a cathode, a modulator electrode for controlling the intensity of the electron stream, a first anode for accelerating the electrons, a second anode and a focussing system for focussing the electron stream into a beam which impinges on the phosphor screen to produce a spot of small cross-sectional area.
In cathode ray tubes of the type designed for television reception, the electrode assembly comprises, in the order named, a cathode, a modulator electrode for controlling the intensity of electron stream, an anode for accelerating the electrons and a foc~lsxing system which usually consists of one or more cylindri-cal electrostatic lenses for focussing the electron stream into a narrow beam of electrons. The electron gun so constructed is operated such that the anode i9 supplied with a low voltage of the range between 200 and 450 volts and the focussing system of, for example, a bi-potential type which consists of two cylindrical electrostatic lenses is maintained at a potential of 4 to 5.5 kilovolts at the beam entry side and at a potential of 20 to 30 kilovolts at the beam leaving side of the system. The electron beam first converges to form an electron crossover point between the modulator electrode and the anode, diverges to a larger diameter, and then pre-focussed by the electri-cal field between the anode and the focussing system and enters the focussing system at a great angle of beam spread until it reaches a region where a final focussing lens is formed, the beam subsequently being caused to converge so as to come to a focus on the phosphor screen and produce a spot of small cross-sectional area. Since the beam enters the focussing system at a large angle of beam spread, the cross-sectional area of the beam in the midst of the focussing system occupies a substantial area of the cross-section of the system and a spot of large cross-sectional area will result due to the spherical aberrations of the system, and ~o-called "blooming"
occurs when the beam current increases.
The increment of the beam spot size is a function of the beam spread angle and of the spherical aber-rations of the main focussing system. The relation between these factors is given by the following equation:
~rsp = M. Cs 3 where, arSp is the increment, M, the magnification factor of the main focussing system, C , the coefficient of spherical aberrations of the system, and 0, the angle of beam spread. On the other hand, the angle of beam spread increases with the beam current and therefore, the beam spot size increases at a higher rate for large beam current than for small beam current. It follows from this that a reduction in the beam spread angle in the beam entry region of the focussing system will result in a reduction in the beam spot size for large beam currentO This is particularly important for the design of a color television cathode ray tube which requires a large beam current.
One form of reducing the beam spread angle employs an intercepting electrode having a beam limiting aperture to limit the cro~s-section Or the electron beam passing therethrough. Thi~ apparently has a drawback in that it wastes a substantial portion of the usable electrons which would be otherwise focussed on the phosphor screen.
In an alternative form of reducing the beam spread angle, the focussing system is maintained at a higher potential with respect to the anode so as to enhance the pre-focussing effect. I-lowever, this results in an increase in the axial length of the focussing system which will cause a halo to appear at the periphery of the beam spot.
In color television cathode ray tubes of the shadow mask type, there is provided a set of three electron gun assemblies, each for producing a beam of electrons for the particular color dot on the screen.
It is therefore necessary that the focussing potential of ~ach electron gun assembly must remain substantially constant over the operating range of the beam current while maintaining the beam spot size to a minimum determined by the particular beam current. This is called focus tracking characteristic.
Therefore, an object of the invention is to provide a narrow electron beam of increased intensity.
Another object is to reduce the angle of beam ~061007 spread in the beam entry region of the focussing system of an electron gun assembly.
A further object of the invention is to provide an electron gun assembly with improved focus tracking character-istic.
In accordance with the present invention, there is provided an electron gun assembly for a cathode ray tube compris-ing, in the order named along the axis of the tube, a cathode, an apertured control electrode located closed to the cathode for controlling the intensity of the electron stream, a first anode in the form of an apertured metal member located close to the control electrode, an apertured second anode located close to the first anode and a third cylindrical focussing anode adjacent to the second anode, said electrodes beins of such con-figuration, and arranged to be maintained at such potentials in operation that the electron stream from the cathode is ~formed into a crossover between the control electrode and the first anode, said second anode being maintained at a lower positive potential than the positive potentials applied to the first and third anodes such that the ratio of potentials applied to the second to first anodes is in the range from 1:1.5 to 1:6.0 so that said electron stream is narrowed at a region adjacent to the third anode by the electric fields between the first, second and third anodes and is allowed to enter the third anode at a small angle of beam spread and focussed thereby into a narrow beam of electrons without loss of electrons as they pass through said first to third anodes.
The invention will be further described with reference to the accompanying drawings, in which:
Fig. 1 is a schematic circuit arrangement in accordance with the invention;
Fig. 2 is a schematic but detailed cross-sectional view of a bi-potential type electrode assembly of a cathode ray tube of the invention suitable for use in the circuit arrangement of the invention;
Figs. 3 and 4 are graphs showing spot diameter versus beam current characteristics of the bi-potential type electrode assembly;
Fig. 5 is a graph showing focus tracking characteristics of the electrode assembly;
Fig. 6 is a graph showing angle of beam spread versus beam current characteristic of the electrode assembly;
Fig. 7 is a graph showing spot size versus potential ratio characteristics of the electrode assembly;
106~007 Fig. o i9 a ~yraph showing follow-up response characteristics of` the electron beam relative to variation of the ratio of potentials applied to the first and second anodes of the electrode assembly;
Fig. 9 is a schematic cross-sectional view of` a uni-potential type electrode assembly in accordance with the invention;
Fig. 10 is a graph showing angle of beam spread versus beam current characteristic of the uni-potential type electrode assembly;
Fig. 11 is a graph showing spot size versus beam current characteristic of the uni-potential type electrode assembly.
Fig. 12 shows the trajectory of the electron stream travelling through the prior art bi-potential type electrode assembly in a simulation test using an IBM-370 computer; and Fig. 13 shows the trajectory of the electron stream travelling through the bi-potential type electrode assembly of the invention in a simulation test using the same computer.
Referring now to Fig. 1, the circuit arrangement incorporating a cathode ray tube having an envelope consisting o~` a cylindrical glass neck portiorl I and conical bulb portion 2 in the approximate shape of a hollow truncated cone closed by a glass faceplate 3 on the inner surface of which is formed a phosphor screen ~.
The neck portion l houses the electrode assembly consisting of a thermionic cathode 5 with heater 6, an apertured modulator or control eLectrode 7 and the focussing means provided in accordance with the invention, conslsting of an apertured metal member first anode 8, a second anode 9 which may be in the form of a plate or a cup as showr. and a main focussing system lO which may be a cylindrical focussing lens system such as uni-potential, bi-potential or tri-potential type. The electrodes within the neck l are connected through leads passing out through the envelope to a potential source 17 for supplying them with the necessary operating potentials. These potentials are such that electrons emitted from the cathode 5 are, as indicated by the dotted lines represen~ing the electron stream (the diameter of the stream being shown exaggerated for the purposes of illustration), formed into a crossover at a region between the modulator electrode 7 and the first anode o.
In accordance with the present invention, the second anode 9 is maintained at a potentia~ lower than ~} the potentials applied to the f`irst anode ~ and the focussing system ]0. The inventiorl will be described in more detail with reference to l~ig. 2 which shows, for example, a bi-potential type focussing system consisting of a third anode 11 and a fourth anode 12.
Specifically, the first anode 8 is maintained at a potential in the range of about Goo to 1,200 volts, preferably from 800 to 1,000 volts,the second anode 9 being maintained at between 200 and l~oo volts, a third anode 11 being at a potential of ~,000 to 7,000 volts and a fourth anode 12 at 20,000 to 30,000 volts.
It was shown in an experiment that with the second anode 9 being at such a lower potential than the potentials applied to the first and third anodes, electrical fields of sharp potential gradient are formed between the first and second anodes and the second and third anodes. With these electrical fields, the stream of electrons subsequent to the crossover point diverges to a larger diameter until it reaches the midpoint region between the second anode 9 and the third anode 11 and then converges to a narrow beam of electrons and enters the third electrode 11 at a small angle (0) of beam spread. This convergence of electrons at the beam entry region of the third anode 11 is found to be a function of the ratio of the potential applied to the second anode 9 to the -- 10 _ 1~)61007 potential applied to the first anode 8 and of the ratio of the potential applied to the third anode 11 to the potential applied to the second anode 9.
The lowering of potential at the second anode 9 with respect to the first and third anodes thus produces a narrowed beam of electrons which slightly diverges and then is caused to converge by the electric field between the third anode 11 and the fourth anode 12 and remains of substantially constant cross-section from that region to the phosphor screen 4.
The ratio of potential at second anode to that applied to first anode suitable for television reception is found to be in the range from 1:1.5 to 1:6.0, preferably from 1:2.0 to 1:5Ø
On the other hand, the ratio of potential applied to the third anode to that applied to the second anode is variable from one ; cathode ray tube to another, because the potential at the third anode will vary according to the screen size. However, the pre-ferred range of the latter ratio is found to be from 1:0.03 to 1 : O . 1 .
It is also found that the aperture diameter of the second anode 9 should be greater than that of the first anode 8 and the preferred ratio of the former to the latter is in the range between 1.5:1 and 3:1.
A uni-potential type electrode assembly is shown in ~ig. 9 as an alternative arrangement in whicl-similar components are indicated by similar numbers.
The uni-potential type focussing system 10 forms a cylindrical lens system consisting of a third anode 13, a fourth anode 14 and a fifth anode 15 which is maintained at the same potential as at third electrode 13 by electrical connection 16. The electrode 14 is maintained at a much lower potential than the third and fifth anodes.
The second anode 9 is maintained at such a lower potential than at the first anode 8 and third anode 13 that the electron stream is formed into a beam of small cross-sectional area and enters the third anode 13 at a small angle of beam spread. The preferred ratio of potential applied to the second anode 9 to the potential applied to the first anode 8 is found tO
be in the range from 1 : 1.5 to 1 : 6 . o, and the pre-ferred ratio Of potential applied to the third anode 13 to that applied to the second anode 9 is found to be in the range from 1 : o.oo6 to 1 : 0.04.
The aperture diameter ratio of the second anode 9 to the first anode 8 should also be in the range of 1.5 : 1 and 3 0 1 as in the bi-potential type electrode assembly.
The fact that the lowering of potential at the second anode with respect to the fir~t and third anodes results in a beam of eLectrons entering at a reduced angle of beam spread with increased electron density is found to be particularly advantageou~ when the electrode assembly is operated at a large beam current as in the case of color television reception.
The invention will be further described with reference to the bi-potential type electrode assembly by way of the following examples to determine the operating range of the electrode~ to achieve the intended result. The structural dimensions of the electrode assembly are only an example and may be varied. Although the operating parameters of the electrode assembly will vary according to the ~truc-tural dimensions of the assembly, the operating rangeof the electrodes is the optimum values regardless of the structural dimensions in so far as one can obtain a beam spot of the minimum cross-sectional area required for a particular dimension.
EXAMPLE I
The bi-potential type electrode assembly has the following structural parameters:
Aperture diameter of modulator electrode (Dm) .... 0.5 mm 106~007 Aperture diameter of l~t anode (1)l) .... o.8 mm Aperture diameter of 2nd anode (D2) .... 1.0 mm Aperture diameter of 3rd anode (D3) .... 2.0 mm Thickness of modulator electrode (~r) .... o. 1 mm Spacing between cathode and modulator electrode .... 0.1 mm Spacing between modulator electrode and Ist anode .... 0.5 mm Spacing between 1st and 2nd anodes .... 0.5 mm Spacing between 2nd and 3rd anodes .... 3.0 mm With these parameters, tlle following potentials were applied to these electrodes:
Vc Vm = -150 volts (cut-off`) Vl = 800 to 1,~00 volts V2 = 200 to 400 volts V3 = 6,ooo to 6,800 volts V4 = 20,000 to 30,000 volts c m' 1' V2, V3 and V4 are the potentials applied to the cathode 5, modulator 7, first anode 8, second anode 9, third anode 11 and fourth anode 12 respectively~ The second anode potential V2 was varied from 200 to 400 volts, that is, the ratio of V2 to Vl - l4 -106~007 was varied from l : 0 to 1 : 6.0 to obtain the minimum spot size for particuLar beam current which was varied up to 2.5 milliamperes. The minimum beam spot size varied from o.6 mm to 2.2 mm in diameter, as shown in Fig. 3.
In order to obtain the minimum beam spot size for the varying beam current, the potential at the third anode was adjusted in the range from 6,000 to 6,800 volts. This range of adjustment represents the focus tracking characteristic of the electrode assembly.
As shown in the solid-line curves of Fig. 5, the range of adjustment is substantially constant over the beam current of up to 2.5 milliamperes.
For comparison purposes, a conventional electron gun assembly of the bi-potential type similar to that shown in Figo 2 of the invention except that the second anode 8 is excluded is tested. The conventional elec-trode assembly has the following structural parameters:
Aperture diameter of modulator electrode ........................... 0.7 to 0.75 mm Aperture diameter of 1st anode ...... 0.7 to 0.75 mm Aperture diameter of 3rd anode ...... 2.0 mm Thickness of modulator electrode .... 0.1 to 0.15 mm Spacing between cathode and modulator electrode ... 0 0.1 to 0.15 mm Spacing between modulator electrode and 1st anode .... 2.5 to 4.0 mm Spacing between 1st and 3rd anodes .... 0.3 to 0.5 mm Potentials applied to these electrodes are as follows:
V = O
Vm = -100 volts (cut-off) Vl = 200 to 450 volts V3 = 4,000 to 5,500 volts V4 = 20,000'to 30,000 volts With these parameters, the beam current was varied up to 2.5 milliamperes. As a result, spot size (diameter) versus beam current characteristics were obtained as shown in curves a, b, and c of Fig. 3, which amount to a reduction in the beam spot size of substantially 40% and compare favorably with the characteristic labelled "prior art".
Simulation tests were conducted using an IBM-370 com-puter in respect of both the prior art and the present electrode assemblies for a beam current of 2.5 milliamperes to determine the trajectory of the electron streams of the two assemblies.
Results are shown in ~igs. 12 and 13. In Fig. 12 the apertures diameter of the first anode is scaled-down to 1/2 compared with the modulator electrode and the third anode is scaled down to 1/2.5 compared with the first 1~61007 anode. Similarly, in Eig. 13, the aperture diameter of the second anode is scaled down to 1/2 and the third anode is scaled down to 1/2.5 compared with the second anode for purposes of clarirication. It iY
appreciated that in ~ig. 13 the electron beam enters the focussing system consisting of the third and fourth anod~s at a small angle of beam spread. At a region adjacent to the focussing electric field between the third and fourth anodes it diverges to its maximum diameter which is favorably compared with the maximum diameter of the electron beam in the equivalent region of the prior art electrode as~embly as shown in l~ig.
12. Therefore, it is shown that the electron beam of the invention is less affected adversely by the spherical aberrations of the focussing electrodeO
EXAMPLE II
A bi-potential type electrode assembly similar in configuration to, but slightly differring in structural dimensions from that used in Example I was operated. The first anode 8 was maintained at 610 volts and the potential a-t second anode 9 was varied from 200 to 400 volts, with the third anode being maintain-ed at a potential in the range of 6.0 to 6.; kilovolts. -106~007 The other parameters were the same as in Example I.
In this example, the potential ratio of V2 to Vl wa~
varied from 1 : 1.5 to 1 : 3Ø The results are shown in Eigs. 4 and 5. The focus tracking charac-teristic shown in dotted-line curves in Ei$. 5 explains that at the potential ratio of 1 : 1.53 of V2 to Vl the adjustment range of the potential at the third anode 11 is from 6.2 to 6.4 kilovolts.
The spot size versus beam current characteristic of the inventicn with the first anode being maintained at a potential of 610 volts is favorably compared with the prior art as shown in Eig. 4, the curve of prior art being the same as that obtained in Example I. The minimum spot size was from o.6 to 2.5 mm in diameterO
EXAMPLE III
The angle of beam spread versus beam current characteristic was obtained and compared with the corresponding characteristic of the prior art. The electrode assembly used in Example I was applied with the following potentials:
Vl = 1,050 volts V2 = 280 volts V3 = 6,ooo volts -~061007 The beam current was varied from 0.l to 2.5 milli-amperes.
The electrode assembly of the prior art as used in Example I was applied with the following potentials:
Vl = 300 volts V3 = 5,000 volts Curves obtained for each of the electrode assemblies are shown in Fig. 6. The angle of beam spread of the present invention is f`avorably compared with that of the prior art.
EXAMPLE IV
The variation of beam spot size was measured f`or a given beam current as the potential ratio of V2 to Vl was varied. As shown in Fig. 7, the spot size remains substantially constant for the beam current of 3.0 milliamperes over the range of potential ratio from 105 to 600.
EXAMPLE V
The response characteristic of the electron beam at a video frequency of 4 MHz was measured for a given beam current as the potential ratio of V2 to Vl was varied. Sinusoidal wave at a frequency of 4 MHz was applied to the modulator electrode and the V~ to V
~061007 ratio was varied up to 6Ø 'I`he amplitude of the beam spot inten~ity was measured by a photodetector and compared with the amplitude of the original waveform applied to the modulator electrode so as to determine how the follow-up response characteristic of the electron beam at the video frequency of 4 Mltz varies with the potential ratio. Data shown in Eig. 8 shows that the ratio of l.5 to 6.0 ensures good response characteristic.
EXAMPLE VI
The uni-potential type electrode assembly has the following structural parameters:
Aperture diameter of modulator electrode .......................... 0.5 mm Aperture diameter of 1st anode ..... 0.7 mm Aperture diameter of 2nd anode ..... 1.5 mm Aperture diameter of 3rd anode ..... 2.0 mm Thickness of modulator electrode .... 0.1 mm Spacing between cathode and modulator electrode .... Ool mm Spacing between modulator electrode and 1st anode .... 0.5 mm Spacing between 1st and 2nd anodes .... 0.5 mm Spacing between 2nd and 3rd anodes .... 3.0 mm With these structural parameters, the following potentials are applied to these electrodes:
c V = 150 volts (cut-off) Vl = 800 to 1,200 volts V2 = 150 to 60o volts V3 = 15,000 to 25,000 volts V4 = -1,000 to +1,000 volts V5 = 15,000 to 25,000 volts ' c' m' Vl, V2, V3, V4 and V5 are the potentials applied to the cathode 5, modulator 7, first anode 8, second anode 9, third anode 13, fourth anode 14 and fifth anode 15 respectively. The angle of beam spread versus beam current characteristic of the uni-potential type was obtained as shown in Fig. 10. For comparison purposes,-the corresponding characteristic of a prior art uni-potential type electrode assembly is plotted on Fig. lOo The reduced beam spread angle for the beam current of 2.0 mm milliamperes ensures that the so called "blooming" can be effectively eliminated when the electrode assembly is operated at a large beam current. The beam spot size versus beam current was obtained aDd compared favorably with prior art as shown in Fig. 11 which amounts to a reduction in the beam spot si~e of substantially 30%.
In cathode ray tubes of the type designed for television reception, the electrode assembly comprises, in the order named, a cathode, a modulator electrode for controlling the intensity of electron stream, an anode for accelerating the electrons and a foc~lsxing system which usually consists of one or more cylindri-cal electrostatic lenses for focussing the electron stream into a narrow beam of electrons. The electron gun so constructed is operated such that the anode i9 supplied with a low voltage of the range between 200 and 450 volts and the focussing system of, for example, a bi-potential type which consists of two cylindrical electrostatic lenses is maintained at a potential of 4 to 5.5 kilovolts at the beam entry side and at a potential of 20 to 30 kilovolts at the beam leaving side of the system. The electron beam first converges to form an electron crossover point between the modulator electrode and the anode, diverges to a larger diameter, and then pre-focussed by the electri-cal field between the anode and the focussing system and enters the focussing system at a great angle of beam spread until it reaches a region where a final focussing lens is formed, the beam subsequently being caused to converge so as to come to a focus on the phosphor screen and produce a spot of small cross-sectional area. Since the beam enters the focussing system at a large angle of beam spread, the cross-sectional area of the beam in the midst of the focussing system occupies a substantial area of the cross-section of the system and a spot of large cross-sectional area will result due to the spherical aberrations of the system, and ~o-called "blooming"
occurs when the beam current increases.
The increment of the beam spot size is a function of the beam spread angle and of the spherical aber-rations of the main focussing system. The relation between these factors is given by the following equation:
~rsp = M. Cs 3 where, arSp is the increment, M, the magnification factor of the main focussing system, C , the coefficient of spherical aberrations of the system, and 0, the angle of beam spread. On the other hand, the angle of beam spread increases with the beam current and therefore, the beam spot size increases at a higher rate for large beam current than for small beam current. It follows from this that a reduction in the beam spread angle in the beam entry region of the focussing system will result in a reduction in the beam spot size for large beam currentO This is particularly important for the design of a color television cathode ray tube which requires a large beam current.
One form of reducing the beam spread angle employs an intercepting electrode having a beam limiting aperture to limit the cro~s-section Or the electron beam passing therethrough. Thi~ apparently has a drawback in that it wastes a substantial portion of the usable electrons which would be otherwise focussed on the phosphor screen.
In an alternative form of reducing the beam spread angle, the focussing system is maintained at a higher potential with respect to the anode so as to enhance the pre-focussing effect. I-lowever, this results in an increase in the axial length of the focussing system which will cause a halo to appear at the periphery of the beam spot.
In color television cathode ray tubes of the shadow mask type, there is provided a set of three electron gun assemblies, each for producing a beam of electrons for the particular color dot on the screen.
It is therefore necessary that the focussing potential of ~ach electron gun assembly must remain substantially constant over the operating range of the beam current while maintaining the beam spot size to a minimum determined by the particular beam current. This is called focus tracking characteristic.
Therefore, an object of the invention is to provide a narrow electron beam of increased intensity.
Another object is to reduce the angle of beam ~061007 spread in the beam entry region of the focussing system of an electron gun assembly.
A further object of the invention is to provide an electron gun assembly with improved focus tracking character-istic.
In accordance with the present invention, there is provided an electron gun assembly for a cathode ray tube compris-ing, in the order named along the axis of the tube, a cathode, an apertured control electrode located closed to the cathode for controlling the intensity of the electron stream, a first anode in the form of an apertured metal member located close to the control electrode, an apertured second anode located close to the first anode and a third cylindrical focussing anode adjacent to the second anode, said electrodes beins of such con-figuration, and arranged to be maintained at such potentials in operation that the electron stream from the cathode is ~formed into a crossover between the control electrode and the first anode, said second anode being maintained at a lower positive potential than the positive potentials applied to the first and third anodes such that the ratio of potentials applied to the second to first anodes is in the range from 1:1.5 to 1:6.0 so that said electron stream is narrowed at a region adjacent to the third anode by the electric fields between the first, second and third anodes and is allowed to enter the third anode at a small angle of beam spread and focussed thereby into a narrow beam of electrons without loss of electrons as they pass through said first to third anodes.
The invention will be further described with reference to the accompanying drawings, in which:
Fig. 1 is a schematic circuit arrangement in accordance with the invention;
Fig. 2 is a schematic but detailed cross-sectional view of a bi-potential type electrode assembly of a cathode ray tube of the invention suitable for use in the circuit arrangement of the invention;
Figs. 3 and 4 are graphs showing spot diameter versus beam current characteristics of the bi-potential type electrode assembly;
Fig. 5 is a graph showing focus tracking characteristics of the electrode assembly;
Fig. 6 is a graph showing angle of beam spread versus beam current characteristic of the electrode assembly;
Fig. 7 is a graph showing spot size versus potential ratio characteristics of the electrode assembly;
106~007 Fig. o i9 a ~yraph showing follow-up response characteristics of` the electron beam relative to variation of the ratio of potentials applied to the first and second anodes of the electrode assembly;
Fig. 9 is a schematic cross-sectional view of` a uni-potential type electrode assembly in accordance with the invention;
Fig. 10 is a graph showing angle of beam spread versus beam current characteristic of the uni-potential type electrode assembly;
Fig. 11 is a graph showing spot size versus beam current characteristic of the uni-potential type electrode assembly.
Fig. 12 shows the trajectory of the electron stream travelling through the prior art bi-potential type electrode assembly in a simulation test using an IBM-370 computer; and Fig. 13 shows the trajectory of the electron stream travelling through the bi-potential type electrode assembly of the invention in a simulation test using the same computer.
Referring now to Fig. 1, the circuit arrangement incorporating a cathode ray tube having an envelope consisting o~` a cylindrical glass neck portiorl I and conical bulb portion 2 in the approximate shape of a hollow truncated cone closed by a glass faceplate 3 on the inner surface of which is formed a phosphor screen ~.
The neck portion l houses the electrode assembly consisting of a thermionic cathode 5 with heater 6, an apertured modulator or control eLectrode 7 and the focussing means provided in accordance with the invention, conslsting of an apertured metal member first anode 8, a second anode 9 which may be in the form of a plate or a cup as showr. and a main focussing system lO which may be a cylindrical focussing lens system such as uni-potential, bi-potential or tri-potential type. The electrodes within the neck l are connected through leads passing out through the envelope to a potential source 17 for supplying them with the necessary operating potentials. These potentials are such that electrons emitted from the cathode 5 are, as indicated by the dotted lines represen~ing the electron stream (the diameter of the stream being shown exaggerated for the purposes of illustration), formed into a crossover at a region between the modulator electrode 7 and the first anode o.
In accordance with the present invention, the second anode 9 is maintained at a potentia~ lower than ~} the potentials applied to the f`irst anode ~ and the focussing system ]0. The inventiorl will be described in more detail with reference to l~ig. 2 which shows, for example, a bi-potential type focussing system consisting of a third anode 11 and a fourth anode 12.
Specifically, the first anode 8 is maintained at a potential in the range of about Goo to 1,200 volts, preferably from 800 to 1,000 volts,the second anode 9 being maintained at between 200 and l~oo volts, a third anode 11 being at a potential of ~,000 to 7,000 volts and a fourth anode 12 at 20,000 to 30,000 volts.
It was shown in an experiment that with the second anode 9 being at such a lower potential than the potentials applied to the first and third anodes, electrical fields of sharp potential gradient are formed between the first and second anodes and the second and third anodes. With these electrical fields, the stream of electrons subsequent to the crossover point diverges to a larger diameter until it reaches the midpoint region between the second anode 9 and the third anode 11 and then converges to a narrow beam of electrons and enters the third electrode 11 at a small angle (0) of beam spread. This convergence of electrons at the beam entry region of the third anode 11 is found to be a function of the ratio of the potential applied to the second anode 9 to the -- 10 _ 1~)61007 potential applied to the first anode 8 and of the ratio of the potential applied to the third anode 11 to the potential applied to the second anode 9.
The lowering of potential at the second anode 9 with respect to the first and third anodes thus produces a narrowed beam of electrons which slightly diverges and then is caused to converge by the electric field between the third anode 11 and the fourth anode 12 and remains of substantially constant cross-section from that region to the phosphor screen 4.
The ratio of potential at second anode to that applied to first anode suitable for television reception is found to be in the range from 1:1.5 to 1:6.0, preferably from 1:2.0 to 1:5Ø
On the other hand, the ratio of potential applied to the third anode to that applied to the second anode is variable from one ; cathode ray tube to another, because the potential at the third anode will vary according to the screen size. However, the pre-ferred range of the latter ratio is found to be from 1:0.03 to 1 : O . 1 .
It is also found that the aperture diameter of the second anode 9 should be greater than that of the first anode 8 and the preferred ratio of the former to the latter is in the range between 1.5:1 and 3:1.
A uni-potential type electrode assembly is shown in ~ig. 9 as an alternative arrangement in whicl-similar components are indicated by similar numbers.
The uni-potential type focussing system 10 forms a cylindrical lens system consisting of a third anode 13, a fourth anode 14 and a fifth anode 15 which is maintained at the same potential as at third electrode 13 by electrical connection 16. The electrode 14 is maintained at a much lower potential than the third and fifth anodes.
The second anode 9 is maintained at such a lower potential than at the first anode 8 and third anode 13 that the electron stream is formed into a beam of small cross-sectional area and enters the third anode 13 at a small angle of beam spread. The preferred ratio of potential applied to the second anode 9 to the potential applied to the first anode 8 is found tO
be in the range from 1 : 1.5 to 1 : 6 . o, and the pre-ferred ratio Of potential applied to the third anode 13 to that applied to the second anode 9 is found to be in the range from 1 : o.oo6 to 1 : 0.04.
The aperture diameter ratio of the second anode 9 to the first anode 8 should also be in the range of 1.5 : 1 and 3 0 1 as in the bi-potential type electrode assembly.
The fact that the lowering of potential at the second anode with respect to the fir~t and third anodes results in a beam of eLectrons entering at a reduced angle of beam spread with increased electron density is found to be particularly advantageou~ when the electrode assembly is operated at a large beam current as in the case of color television reception.
The invention will be further described with reference to the bi-potential type electrode assembly by way of the following examples to determine the operating range of the electrode~ to achieve the intended result. The structural dimensions of the electrode assembly are only an example and may be varied. Although the operating parameters of the electrode assembly will vary according to the ~truc-tural dimensions of the assembly, the operating rangeof the electrodes is the optimum values regardless of the structural dimensions in so far as one can obtain a beam spot of the minimum cross-sectional area required for a particular dimension.
EXAMPLE I
The bi-potential type electrode assembly has the following structural parameters:
Aperture diameter of modulator electrode (Dm) .... 0.5 mm 106~007 Aperture diameter of l~t anode (1)l) .... o.8 mm Aperture diameter of 2nd anode (D2) .... 1.0 mm Aperture diameter of 3rd anode (D3) .... 2.0 mm Thickness of modulator electrode (~r) .... o. 1 mm Spacing between cathode and modulator electrode .... 0.1 mm Spacing between modulator electrode and Ist anode .... 0.5 mm Spacing between 1st and 2nd anodes .... 0.5 mm Spacing between 2nd and 3rd anodes .... 3.0 mm With these parameters, tlle following potentials were applied to these electrodes:
Vc Vm = -150 volts (cut-off`) Vl = 800 to 1,~00 volts V2 = 200 to 400 volts V3 = 6,ooo to 6,800 volts V4 = 20,000 to 30,000 volts c m' 1' V2, V3 and V4 are the potentials applied to the cathode 5, modulator 7, first anode 8, second anode 9, third anode 11 and fourth anode 12 respectively~ The second anode potential V2 was varied from 200 to 400 volts, that is, the ratio of V2 to Vl - l4 -106~007 was varied from l : 0 to 1 : 6.0 to obtain the minimum spot size for particuLar beam current which was varied up to 2.5 milliamperes. The minimum beam spot size varied from o.6 mm to 2.2 mm in diameter, as shown in Fig. 3.
In order to obtain the minimum beam spot size for the varying beam current, the potential at the third anode was adjusted in the range from 6,000 to 6,800 volts. This range of adjustment represents the focus tracking characteristic of the electrode assembly.
As shown in the solid-line curves of Fig. 5, the range of adjustment is substantially constant over the beam current of up to 2.5 milliamperes.
For comparison purposes, a conventional electron gun assembly of the bi-potential type similar to that shown in Figo 2 of the invention except that the second anode 8 is excluded is tested. The conventional elec-trode assembly has the following structural parameters:
Aperture diameter of modulator electrode ........................... 0.7 to 0.75 mm Aperture diameter of 1st anode ...... 0.7 to 0.75 mm Aperture diameter of 3rd anode ...... 2.0 mm Thickness of modulator electrode .... 0.1 to 0.15 mm Spacing between cathode and modulator electrode ... 0 0.1 to 0.15 mm Spacing between modulator electrode and 1st anode .... 2.5 to 4.0 mm Spacing between 1st and 3rd anodes .... 0.3 to 0.5 mm Potentials applied to these electrodes are as follows:
V = O
Vm = -100 volts (cut-off) Vl = 200 to 450 volts V3 = 4,000 to 5,500 volts V4 = 20,000'to 30,000 volts With these parameters, the beam current was varied up to 2.5 milliamperes. As a result, spot size (diameter) versus beam current characteristics were obtained as shown in curves a, b, and c of Fig. 3, which amount to a reduction in the beam spot size of substantially 40% and compare favorably with the characteristic labelled "prior art".
Simulation tests were conducted using an IBM-370 com-puter in respect of both the prior art and the present electrode assemblies for a beam current of 2.5 milliamperes to determine the trajectory of the electron streams of the two assemblies.
Results are shown in ~igs. 12 and 13. In Fig. 12 the apertures diameter of the first anode is scaled-down to 1/2 compared with the modulator electrode and the third anode is scaled down to 1/2.5 compared with the first 1~61007 anode. Similarly, in Eig. 13, the aperture diameter of the second anode is scaled down to 1/2 and the third anode is scaled down to 1/2.5 compared with the second anode for purposes of clarirication. It iY
appreciated that in ~ig. 13 the electron beam enters the focussing system consisting of the third and fourth anod~s at a small angle of beam spread. At a region adjacent to the focussing electric field between the third and fourth anodes it diverges to its maximum diameter which is favorably compared with the maximum diameter of the electron beam in the equivalent region of the prior art electrode as~embly as shown in l~ig.
12. Therefore, it is shown that the electron beam of the invention is less affected adversely by the spherical aberrations of the focussing electrodeO
EXAMPLE II
A bi-potential type electrode assembly similar in configuration to, but slightly differring in structural dimensions from that used in Example I was operated. The first anode 8 was maintained at 610 volts and the potential a-t second anode 9 was varied from 200 to 400 volts, with the third anode being maintain-ed at a potential in the range of 6.0 to 6.; kilovolts. -106~007 The other parameters were the same as in Example I.
In this example, the potential ratio of V2 to Vl wa~
varied from 1 : 1.5 to 1 : 3Ø The results are shown in Eigs. 4 and 5. The focus tracking charac-teristic shown in dotted-line curves in Ei$. 5 explains that at the potential ratio of 1 : 1.53 of V2 to Vl the adjustment range of the potential at the third anode 11 is from 6.2 to 6.4 kilovolts.
The spot size versus beam current characteristic of the inventicn with the first anode being maintained at a potential of 610 volts is favorably compared with the prior art as shown in Eig. 4, the curve of prior art being the same as that obtained in Example I. The minimum spot size was from o.6 to 2.5 mm in diameterO
EXAMPLE III
The angle of beam spread versus beam current characteristic was obtained and compared with the corresponding characteristic of the prior art. The electrode assembly used in Example I was applied with the following potentials:
Vl = 1,050 volts V2 = 280 volts V3 = 6,ooo volts -~061007 The beam current was varied from 0.l to 2.5 milli-amperes.
The electrode assembly of the prior art as used in Example I was applied with the following potentials:
Vl = 300 volts V3 = 5,000 volts Curves obtained for each of the electrode assemblies are shown in Fig. 6. The angle of beam spread of the present invention is f`avorably compared with that of the prior art.
EXAMPLE IV
The variation of beam spot size was measured f`or a given beam current as the potential ratio of V2 to Vl was varied. As shown in Fig. 7, the spot size remains substantially constant for the beam current of 3.0 milliamperes over the range of potential ratio from 105 to 600.
EXAMPLE V
The response characteristic of the electron beam at a video frequency of 4 MHz was measured for a given beam current as the potential ratio of V2 to Vl was varied. Sinusoidal wave at a frequency of 4 MHz was applied to the modulator electrode and the V~ to V
~061007 ratio was varied up to 6Ø 'I`he amplitude of the beam spot inten~ity was measured by a photodetector and compared with the amplitude of the original waveform applied to the modulator electrode so as to determine how the follow-up response characteristic of the electron beam at the video frequency of 4 Mltz varies with the potential ratio. Data shown in Eig. 8 shows that the ratio of l.5 to 6.0 ensures good response characteristic.
EXAMPLE VI
The uni-potential type electrode assembly has the following structural parameters:
Aperture diameter of modulator electrode .......................... 0.5 mm Aperture diameter of 1st anode ..... 0.7 mm Aperture diameter of 2nd anode ..... 1.5 mm Aperture diameter of 3rd anode ..... 2.0 mm Thickness of modulator electrode .... 0.1 mm Spacing between cathode and modulator electrode .... Ool mm Spacing between modulator electrode and 1st anode .... 0.5 mm Spacing between 1st and 2nd anodes .... 0.5 mm Spacing between 2nd and 3rd anodes .... 3.0 mm With these structural parameters, the following potentials are applied to these electrodes:
c V = 150 volts (cut-off) Vl = 800 to 1,200 volts V2 = 150 to 60o volts V3 = 15,000 to 25,000 volts V4 = -1,000 to +1,000 volts V5 = 15,000 to 25,000 volts ' c' m' Vl, V2, V3, V4 and V5 are the potentials applied to the cathode 5, modulator 7, first anode 8, second anode 9, third anode 13, fourth anode 14 and fifth anode 15 respectively. The angle of beam spread versus beam current characteristic of the uni-potential type was obtained as shown in Fig. 10. For comparison purposes,-the corresponding characteristic of a prior art uni-potential type electrode assembly is plotted on Fig. lOo The reduced beam spread angle for the beam current of 2.0 mm milliamperes ensures that the so called "blooming" can be effectively eliminated when the electrode assembly is operated at a large beam current. The beam spot size versus beam current was obtained aDd compared favorably with prior art as shown in Fig. 11 which amounts to a reduction in the beam spot si~e of substantially 30%.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electron gun assembly for a cathode ray tube which comprises, in the order named along the axis of the tube, a cathode for emitting in operation an electron stream, an apertured modulator electrode located close to the cathode for controlling the intensity of the electron stream, a first anode in the form of an apertured metal member located close to the modulator electrode, an apertured second anode located close to the first anode and a third cylindrical focusing anode adja-cent to the second anode, and a fourth cylindrical focusing anode each of said third and fourth said cylindrical focusing anodes having an axial bore positioned coaxial with the tube axis and dimensioned for permitting the electron stream to pass there-through unobstructed and without intersecting said cylindrical focusing anodes, said electrodes being of such configuration, and arranged to be maintained at such potentials in operation of the arrangement that the electron stream from the cathode is formed into a crossover between the modulator electrode and the first anode, means to effect in operation a ratio of potential applied to the second anode to the potential applied to the first anode in the range between 1:1.5 and 1:6.0 and the ratio of potential applied to the third anode to the potential applied to the second anode being in the range between 1:0.03 and 1:0.1 to define a first electrostatic lens between said first, second and third anodes effective to narrow said electron stream at a region adjacent to the third anode by the electric fields esta-blished between the first and second anodes and the second and third anodes and to enter the third anode at a small angle of beam spread, said fourth anode defining in operation a second electrostatic lens between said third and fourth anodes to focus said electron stream into a narrow beam of electrons whose cross-section on the screen of the tube is small and there is no electro-static lens-forming effect on the beam of electrons that leaves said fourth anode.
2. An assembly according to claim 1, wherein the ratio of potential applied to the second anode to potential applied to the first anode is in the range between 1:2.0 and 1:5.0 and the ratio of potential applied to the third anode to potential applied to the second anode is in the range between 1:0.03 and 1:0.1.
3. An electron gun assembly as claimed in claim 1 or 2, including means to apply a potential to said fourth anode substantially in a range from 20 kilovolts to 30 kilovolts.
4. An electron gun assembly, comprising a cathode operable to emit electrons; a modulator electrode positioned adjacent said cathode and having an aperture therethrough for defining an electron stream path along an axis from said cathode and through said modulator electrode aperture, said modulator electrode being receptive in use of modulation signals for con-trolling an intensity of an electron stream emitted from said cathode and passing through said modulator electrode aperture along said axis; a first anode positioned downstream from said modulator electrode and having an aperture aligned with said modulator electrode aperture along said axis to permit the electron stream to pass therethrough, said first anode aperture being of a sufficient dimension to permit the electron stream to pass therethrough without intersecting said first anode; a second anode positioned downstream from said cathode and having an aperture aligned with said first anode aperture along said axis to permit the electron stream to pass therethrough, said second anode aperture being of a sufficient dimension to permit the electron stream to pass therethrough without intersecting said second anode; and a bi-potential focusing system positioned downstream from said second anode along said axis for focusing the electron stream into a narrow focused beam of electrons, said bi-potential focusing system comprising a third anode downstream from said second anode and a fourth anode downstream from said third anode, said third and fourth anodes each com-prising cylindrical electodes having respective axial bores aligned along said axis for permitting the stream of electrons to pass therethrough and for focusing the same, said bores being dimensioned to permit the beam of electrons to pass therethrough unobstructed and without intersecting either of said third and fourth electrodes, wherein said anodes are biased in use at potentials effective to form a crossover point in the electron stream between said modulator electrode and said first electrode, and means to effect in operation a ratio of potential applied to the second anode to the potential applied to the first anode in the range between 1:1.5 to 1:6.0, and the ratio of the potential applied to the third anode to the potential applied to the second anode in the range between 1:0.03 to 1:0.1 for focussing the electron stream into a narrow electron beam, the potential applied to said fourth anode being such that there is no lens forming effect upon the electron beam leaving said fourth anode.
5. An electron gun assembly as claimed in claim 4, including means to apply a potential to said fourth anode sub-stantially in a range from 20 kilovolts to 30 kilovolts.
6. A method of operating a cathode ray tube having a faceplate carrying thereon a phosphor screen, and an electron gun comprising a cathode operable to emit electrons, a modu-lator electrode positioned adjacent the cathode and having an aperture therethrough for defining an electron stream path along an axis from the cathode through the modulator electrode aperture and toward the screen, a first anode positioned downstream from the modulator electrode and having an aperture along the axis and being of a sufficient dimension to permit the electron stream to pass therethrough without intersecting the first anode, a second anode positioned downstream from the first anode and having an anode aligned with the first anode aperture along the axis and being of a sufficient dimension to permit the electron stream to pass therethrough without intersecting the second anode, and a bipotential focusing system positioned downstream from the second anode along the axis for focusing the electron stream into a narrow focused beam of electrons and comprising cylindrical third and fourth anodes each having an axial bore aligned along the axis and dimensioned for permitting the stream of electrons to pass therethrough unobstructed, which method comprises: operat-ing the cathode to emit electrons; and relatively biasing said anodes to form a crossover point in the stream of electrons between the modulator electrode and the first anode while, main-taining the ratio of potential applied to the second anode to the potential applied to the first anode in the range between 1:1.5 to 1:6.0, maintaining the ratio of potential applied to the third anode to the potential applied to the second anode in the range between 1:0.03 to 1:0.1 and maintaining the fourth anode at a potential effective to define an electrostatic lens between said third and fourth anodes to focus the electron stream into a narrow beam of electrons whose cross section is small and there is no electrostatic lens-forming effect on the beam of electrons that leaves said fourth anode.
7. A method according to claim 6, wherein the second anode potential to first anode potential ratio is within the range between 1:2.0 to 1:5.0, and the third anode potential to second anode potential ratio is within the range between 1:0.03 to 1:0.1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5707974A JPS5522906B2 (en) | 1974-05-20 | 1974-05-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1061007A true CA1061007A (en) | 1979-08-21 |
Family
ID=13045455
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA215,759A Expired CA1061007A (en) | 1974-05-20 | 1974-12-11 | Electric circuit arrangements incorporating cathode ray tubes |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4287450A (en) |
| JP (1) | JPS5522906B2 (en) |
| CA (1) | CA1061007A (en) |
| DE (1) | DE2459091C3 (en) |
| GB (1) | GB1460120A (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5285414A (en) * | 1976-01-09 | 1977-07-15 | Nippon Hoso Kyokai <Nhk> | Image pickup tube |
| US4124810A (en) * | 1977-06-06 | 1978-11-07 | Rca Corporation | Electron gun having a distributed electrostatic lens |
| US4318027A (en) | 1978-04-12 | 1982-03-02 | Rca Corporation | High potential, low magnification electron gun |
| AU4515779A (en) * | 1978-04-12 | 1979-10-18 | Rca Corp. | Electron gun |
| FR2456387A1 (en) * | 1979-05-08 | 1980-12-05 | Mitsubishi Electric Corp | CATHODE RAY TUBE USED AS A LIGHT SOURCE |
| US4334170A (en) * | 1979-09-28 | 1982-06-08 | Zenith Radio Corporation | Means and method for providing optimum resolution of T.V. cathode ray tube electron guns |
| JPS56133625U (en) * | 1980-03-12 | 1981-10-09 | ||
| US4350925A (en) * | 1980-07-09 | 1982-09-21 | Rca Corporation | Main lens assembly for an electron gun |
| GB2084394B (en) * | 1980-07-30 | 1985-03-06 | Matsushita Electronics Corp | Cathode-ray tube driving apparatus |
| US4409514A (en) * | 1981-04-29 | 1983-10-11 | Rca Corporation | Electron gun with improved beam forming region |
| US4498028A (en) * | 1981-09-28 | 1985-02-05 | Zenith Electronics Corporation | Ultra-short LoBi electron gun for very short cathode ray tubes |
| US4514659A (en) * | 1982-03-04 | 1985-04-30 | Rca Corporation | Inline electron gun for high resolution color display tube |
| US4496877A (en) * | 1982-04-06 | 1985-01-29 | Zenith Electronics Corporation | Unipotential electron gun for short cathode ray tubes |
| NL8204185A (en) * | 1982-10-29 | 1984-05-16 | Philips Nv | CATHED BEAM TUBE. |
| JPS59111237A (en) * | 1982-12-16 | 1984-06-27 | Matsushita Electronics Corp | Cathode ray tube device |
| US4591760A (en) * | 1983-03-25 | 1986-05-27 | Matsushita Electronics Corporation | Cathode ray tube apparatus |
| DE19856384A1 (en) * | 1998-12-07 | 2000-06-08 | Siemens Ag | Method and circuit arrangement for regulating the operating point of a cathode ray tube |
| US6987367B2 (en) | 2003-06-10 | 2006-01-17 | Kabushiki Kaisha Toshiba | Cathode-ray tube |
| JP4795883B2 (en) * | 2006-07-21 | 2011-10-19 | 株式会社日立ハイテクノロジーズ | Pattern inspection / measurement equipment |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US25127A (en) * | 1859-08-16 | Improvement in mole-plows | ||
| USRE25127E (en) * | 1962-02-20 | Cathode-ray tube | ||
| GB759944A (en) * | 1954-03-02 | 1956-10-24 | Gen Electric Co Ltd | Improvements in or relating to electric circuit arrangements incorporating cathode ray tubes |
| US2935636A (en) * | 1955-10-31 | 1960-05-03 | Rca Corp | Electron gun structure |
| US2975315A (en) * | 1957-03-13 | 1961-03-14 | Rauland Corp | Cathode-ray tube |
| US3417199A (en) * | 1963-10-24 | 1968-12-17 | Sony Corp | Cathode ray device |
| US3995194A (en) * | 1974-08-02 | 1976-11-30 | Zenith Radio Corporation | Electron gun having an extended field electrostatic focus lens |
-
1974
- 1974-05-20 JP JP5707974A patent/JPS5522906B2/ja not_active Expired
- 1974-12-11 CA CA215,759A patent/CA1061007A/en not_active Expired
- 1974-12-13 GB GB5402074A patent/GB1460120A/en not_active Expired
- 1974-12-13 DE DE2459091A patent/DE2459091C3/en not_active Expired
-
1976
- 1976-11-09 US US05/739,868 patent/US4287450A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US4287450A (en) | 1981-09-01 |
| GB1460120A (en) | 1976-12-31 |
| DE2459091A1 (en) | 1975-12-04 |
| JPS50158274A (en) | 1975-12-22 |
| DE2459091C3 (en) | 1982-05-13 |
| DE2459091B2 (en) | 1981-08-20 |
| JPS5522906B2 (en) | 1980-06-19 |
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